1. Field of the Invention
This invention relates to processes and intermediates for manufacturing fused heterocyclic-type compounds, such as thienopyridine-based kinase inhibitor compounds, and to processes and intermediates for preparing intermediates that are useful in the manufacture of fused heterocyclic-type compounds, such as thienopyridine-based kinase inhibitor compounds, particularly at an industrial level. Fused heterocyclic-type compounds have been found to be useful to inhibit protein tyrosine kinase activity. In particular, fused heterocyclic-type compounds, such as thienopyridine-based compounds, have been found useful to inhibit the protein tyrosine kinase activity of growth factor receptors, resulting in the inhibition of receptor signaling; for example, the inhibition of VEGF receptor signaling and HGF receptor signaling. Fused heterocyclic-type compounds have been found to be useful in the treatment of cancer by inhibiting protein tyrosine kinase activity. The pharmaceutical compositions that comprise these compounds are also useful in the treatment of diseases, other than cancer, which are associated with signal transduction pathways operating through growth factor and anti-angiogenesis receptors such as c-Met.
2. Summary of the Related Art
Tyrosine kinases may be classified as growth factor receptor (e.g. EGFR, PDGFR, FGFR and erbB2) or non-receptor (e.g. c-src and bcr-abl) kinases. The receptor type tyrosine kinases make up about 20 different subfamilies. The non-receptor type tyrosine kinases make up numerous subfamilies. These tyrosine kinases have diverse biological activity. Receptor tyrosine kinases are large enzymes that span the cell membrane and possess an extracellular binding domain for growth factors, a transmembrane domain, and an intracellular portion that functions as a kinase to phosphorylate a specific tyrosine residue in proteins and hence to influence cell proliferation. Aberrant or inappropriate protein kinase activity can contribute to the rise of disease states associated with such aberrant kinase activity.
Angiogenesis is an important component of certain normal physiological processes such as embryogenesis and wound healing, but aberrant angiogenesis contributes to some pathological disorders and in particular to tumor growth. VEGF-A (vascular endothelial growth factor A) is a key factor promoting neovascularization (angiogenesis) of tumors. VEGF induces endothelial cell proliferation and migration by signaling through two high affinity receptors, the fms-like tyrosine kinase receptor, Flt-1, and the kinase insert domain-containing receptor, KDR. These signaling responses are critically dependent upon receptor dimerization and activation of intrinsic receptor tyrosine kinase (RTK) activity. The binding of VEGF as a disulfide-linked homodimer stimulates receptor dimerization and activation of the RTK domain. The kinase activity autophosphorylates cytoplasmic receptor tyrosine residues, which then serve as binding sites for molecules involved in the propagation of a signaling cascade. Although multiple pathways are likely to be elucidated for both receptors, KDR signaling is most extensively studied, with a mitogenic response suggested to involve ERK-1 and ERK-2 mitogen-activated protein kinases.
Disruption of VEGF receptor signaling is a highly attractive therapeutic target in cancer, as angiogenesis is a prerequisite for all solid tumor growth, and that the mature endothelium remains relatively quiescent (with the exception of the female reproductive system and wound healing). A number of experimental approaches to inhibiting VEGF signaling have been examined, including use of neutralizing antibodies, receptor antagonists, soluble receptors, antisense constructs and dominant-negative strategies.
Despite the attractiveness of anti-angiogenic therapy by VEGF inhibition alone, several issues may limit this approach. VEGF expression levels can themselves be elevated by numerous diverse stimuli and perhaps most importantly, the hypoxic state of tumors resulting from VEGFr inhibition, can lead to the induction of factors that themselves promote tumor invasion and metastasis thus, potentially undermining the impact of VEGF inhibitors as cancer therapeutics.
The HGF (hepatocyte growth factor) and the HGF receptor, c-Met, are implicated in the ability of tumor cells to undermine the activity of VEGF inhibition. HGF derived from either stromal fibroblasts surrounding tumor cells or expressed from the tumor itself has been suggested to play a critical role in tumor angiogenesis, invasion and metastasis. For example, invasive growth of certain cancer cells is drastically enhanced by tumor-stromal interactions involving the HGF/c-Met (HGF receptor) pathway. HGF, which was originally identified as a potent mitogen for hepatocytes, is primarily secreted from stromal cells, and the secreted HGF can promote motility and invasion of various cancer cells that express c-Met in a paracrine manner. Binding of HGF to c-Met leads to receptor phosphorylation and activation of Ras/mitogen-activated protein kinase (MAPK) signaling pathway, thereby enhancing malignant behaviors of cancer cells. Moreover, stimulation of the HGF/c-Met pathway itself can lead to the induction of VEGF expression, itself contributing directly to angiogenic activity.
Biological agents, such as ribozymes, antibodies and antisense RNA targeting either HGF or Met have been shown to inhibit tumorogenesis (Stabile et al., (2004) Gene Therapy, 11:325-335; Jiang et al., (2003) Clin. Cancer Res., 9:4274-4281; and Genentech U.S. Pat. No. 6,214,344).
Thus, anti-tumor and/or anti-angiogenic strategies or approaches that target either or both VEGF/VEGFr signaling and HGF/c-Met signaling may circumvent the ability of tumor cells to overcome VEGF inhibition alone and may represent improved cancer therapeutics.